Several scientific theories
have been proposed to explain the origins of the human races. The most
prevalent theory to explain the origin of the races is that increased
melanin protected people from ultraviolet radiation in the tropics. The
problem with this theory is that the cancer that results from excessive UV
exposure almost always occurs after the reproductive years. Therefore, the
death of people after their Functional and physical units of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.genes have already been passed on could never
be selected by evolution. Another theory states that peoples from Northern
latitudes must have reduced pigment in their skin to form enough vitamin
D3 under the reduced solar luminosity found at the higher latitudes. One
problem with this theory is that the Inuits (Eskimos) have dark skin, but
live in high latitudes. The most likely theory is that people have
selectively chosen to breed with others who look like them. As the
perception of beauty has changed, populations have slowly drifted towards
the current racial patterns that we now observe.

http://www.godandscience.org/evolution/sld105.html
Last Modified June 21, 2006